1. Field of the Invention
This invention relates to 1,2,3,5-tetrahydroimidazothienopyrimidin-2-ones represented by the formula (I): ##STR2## wherein one of Z.sub.1, Z.sub.2 and Z.sub.3 is a sulfur atom and the remaining two of Z.sub.1, Z.sub.2 and Z.sub.3 represent CH, R.sub.1 and R.sub.2 each represents a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, a phenyl group, a chlorine atom or, when taken together R.sub.1 and R.sub.2 represent an alkylene chain of 3 to 5 carbon atoms, R.sub.3 represents a hydrogen atom or an alkyl group having 1 to 5 carbon atoms, and the pharmaceutically acceptable acid addition salts thereof.
2. Description of the Prior Art
Hitherto, anti-thrombotic agents having an imidazopyrimidine structure have been reported in literatures. For example, W. N. Beverung et al, U.S. Pat. No. 3,932,407 discloses 1,2,3,5-tetrahydroimidazo[2,1-b]quinazolin-2-ones represented by the formula: ##STR3## wherein R.sub.1 represents a hydrogen atom or an alkyl group, and R.sub.2 and R.sub.3 each represents a hydrogen atom, an alkyl group or a halogen atom. However, these compounds have not proved satisfactory for clinical use in preventing thrombosis because of their side effects such as hypotensive activity.
P. Blaskiewicz et al, German Offenlegungsschrift No. 2,411,273 discloses the compounds represented by the formula: ##STR4## but this compound is reported as having an anti-inflammatory activity. Also, C. F. Sauter et al, Monatsh. Chem., 109, 53 (1978) discloses the compounds having the formula: ##STR5## wherein R.sub.1 and R.sub.2 each represents --CH.sub.3 or, when taken together, R.sub.1 and R.sub.2 represent --CH.sub.2 CH.sub.2 CH.sub.2 CH.sub.2 --, but blood platelet antiaggregatory activity is not reported for the above compounds.